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How to lay decking

How to lay decking
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Deck out your garden with some beautiful decking. It makes a great area for entertaining, relaxing and putting lots of plants in pots. What’s more, with this simple step-by-step guide it’s easier than you think:

1. Plan out your decking area

The first thing to think about is where you want your decking to go. Having figured this out you then need to draw a to-scale plan on a piece of paper – marking down all the permanent features like your house, walls and manhole covers.

Whilst planning, don’t forget that deck boards placed at right angles to your house draw the eye into the garden beyond, while boards fixed parallel to the wall tend to emphasise the width of the deck.

IMPORTANT: Make sure that the top level of any new decking attached to your house wall is at least 150mm below the damp-proof course in order to meet the current building regulations.

2. Measure up

Having made your scale plan, work out the area of your deck in square metres (m2). Each pack of decking shows the area it covers. So simply divide the area of your deck by the area covered by one pack to see how many packs you need.

Also, work out how many posts and rails you need. If you’re in any doubt just ask a member of staff for help – make sure you bring your plan with you.

3. Prepare the ground

Using pegs and string mark out your decking area. Then clear all turf and weeds from the spot and firm down the ground.

Next, lay a deck fabric over the earth to prevent weeds from growing up through the deck in the future. This fabric can be pegged or weighed down with concrete or paving slabs.

The framework of your deck needs to be laid onto concrete foundations rather than directly onto the soil. You can either lay down concrete for this or use concrete paving slabs – which is easier.

If using slabs, place them in a grid pattern with each slab positioned about 1.4m from the next. These will support the timber joists that hold the boards. Don’t forget to use a spirit level to make sure the deck slopes away slightly (allow a 10mm drop for every metre).

4. Build the framework

To form the outer frame of the deck use joists (150mm high x 50mm wide). Then rest these on top of the levelled concrete or slabs.

Fix the joists together using 100mm rustproof screws and external wood glue. Use one screw on the top edge of the joist and two screws on the sides.

If you’re attaching the deck to your house, screw the first joist to the wall but put plenty of stainless steel washers between the joist and the wall to leave a gap of at least 10mm.

As soon as you’ve finished the outer framework, put long joists inside spaced at 400mm intervals and screw to the frame (these should be fitted at right angles to the finished deck boards, just like an internal floor).

Remember to treat any new cuts in the wood with a timber preservative.

5. Fix the deck boards

Once all the joists are in place, the finished framework should be completely rigid.

Start laying the deck boards next to the house. Lay about six boards at a time, leaving 5mm spaces between boards (about the width of a screw). This is essential for ventilation and allows for expansion in wet weather.

It’s best to use stainless steel screws so that rust stains don’t spoil your decking. Pre-drill your screw holes to reduce the chances of splitting the wood.

Then fix the ends of each board first, before screwing the centre of the board to every joist in between. If the deck is wider than the length of the deck board being used, you’ll need to stagger the boards – remember to join boards over a joist.

6. Vary the design

You don’t have to stick to straight lines on your decking. Boards can be fitted diagonally or cut to form herringbone patterns.

If you have a raised deck that’s over 60cm high, then you must add a deck railing around the edge to form a safety barrier.

7. Add the finishing touches

Deck boards are pressure treated with a long-lasting preservative treatment but the colour will fade after a few months.

You can either leave your deck to age naturally or treat it with an exterior penetrating oil that soaks into the wood rather than sitting on the surface. These come in all kinds of shades and can be brushed, sprayed or rollered onto the boards.

Top Tip

Make sure you use an end coat wood preservative on all sawn wood and drill holes – it will make your beautiful decking last longer.